Cohesity – Cohesity Cluster Virtual Edition ESXi – A Few Notes

I’ve covered the Cohesity appliance deployment in a howto article previously. I’ve also made use of the VMware-compatible Virtual Edition in our lab to test things like cluster to cluster replication and cloud tiering. The benefits of virtual appliances are numerous. They’re generally easy to deploy, don’t need dedicated hardware, can be re-deployed quickly when you break something, and can be a quick and easy way to validate a particular process or idea. They can also be a problem with regards to performance, and are at the mercy of the platform administrator to a point. But aren’t we all? With 6.1, Cohesity have made available a clustered virtual edition (the snappily titled Cohesity Cluster Virtual Edition ESXi). If you have access to the documentation section of the Cohesity support site, there’s a PDF you can download that explains everything. I won’t go into too much detail but there are a few things to consider before you get started.

 

Specifications

Base Appliance 

Just like the non-clustered virtual edition, there’s a small and large configuration you can choose from. The small configuration supports up to 8TB for the Data disk, while the large configuration supports up to 16TB for the Data disk. The small config supports 4 vCPUs and 16GB of memory, while the large configuration supports 8 vCPUs and 32GB of memory.

Disk Configuration

Once you’ve deployed the appliance, you’ll need to add the Metadata disk and Data disk to each VM. The Metadata disk should be between 512GB and 1TB. For the large configuration, you can also apparently configure 2x 512GB disks, but I haven’t tried this. The Data disk needs to be between 512GB and 8TB for the small configuration and up to 16TB for the large configuration (with support for 2x 8TB disks). Cohesity recommends that these are formatted as Thick Provision Lazy Zeroed and deployed in Independent – Persistent mode. Each disk should be attached to its own SCSI controller as well, so you’ll have the system disk on SCSI 0:0, the Metadata disk on SCSI 1:0, and so on.

I did discover a weird issue when deploying the appliance on a Pure Storage FA-450 array in the lab. In vSphere this particular array’s datastore type is identified by vCenter as “Flash”. For my testing I had a 512GB Metadata disk and 3TB Data disk configured on the same datastore, with the three nodes living on three different datastores on the FlashArray. This caused errors with the cluster configuration, with the configuration wizard complaining that my SSD volumes were too big.

I moved the Data disk (with storage vMotion) to an all flash Nimble array (that for some reason was identified by vSphere as “HDD”) and the problem disappeared. Interestingly I didn’t have this problem with the single node configuration of 6.0.1 deployed with the same configuration. I raised a ticket with Cohesity support and they got back to me stating that this was expected behaviour in 6.1.0a. They tell me, however, that they’ve modified the behaviour of the configuration routine in an upcoming version so fools like me can run virtualised secondary storage on primary storage.

Erasure Coding

You can configure the appliance for increased resiliency at the Storage Domain level as well. If you go to Platform – Cluster – Storage Domains you can modify the DefaultStorageDomain (and other ones that you may have created). Depending on the size of the cluster you’ve deployed, you can choose the number of failures to tolerate and whether or not you want erasure coding enabled.

You can also decide whether you want EC to be a post-process activity or something that happens inline.

 

Process

Once you’ve deployed (a minimum) 3 copies of the Clustered VE, you’ll need to manually add Metadata and Data disks to each VM. The specifications for these are listed above. Fire up the VMs and go to the IP of one of the nodes. You’ll need to log in as the admin user with the appropriate password and you can then start the cluster configuration.

This bit is pretty much the same as any Cohesity cluster deployment, and you’ll need to specify things like a hostname for the cluster partition. As always, it’s a good idea to ensure your DNS records are up to date. You can get away with using IP addresses but, frankly, people will talk about you behind your back if you do.

At this point you can also decide to enable encryption at the cluster level. If you decide not to enable it you can do this on a per Domain basis later.

Click on Create Cluster and you should see something like the following screen.

Once the cluster is created, you can hit the virtual IP you’ve configured, or any one of the attached nodes, to log in to the cluster. Once you log in, you’ll need to agree to the EULA and enter a license key.

 

Thoughts

The availability of virtual appliance versions for storage and data protection solutions isn’t a new idea, but it’s certainly one I’m a big fan of. These things give me an opportunity to test new code releases in a controlled environment before pushing updates into my production environment. It can help with validating different replication topologies quickly, and validating other configuration ideas before putting them into the wild (or in front of customers). Of course, the performance may not be up to scratch for some larger environments, but for smaller deployments and edge or remote office solutions, you’re only limited by the available host resources (which can be substantial in a lot of cases). The addition of a clustered version of the virtual edition for ESXi and Hyper-V is a welcome sight for those of us still deploying on-premises Cohesity solutions (I think the Azure version has been clustered for a few revisions now). It gets around the main issue of resiliency by having multiple copies running, and can also address some of the performance concerns associated with running virtual versions of the appliance. There are a number of reasons why it may not be the right solution for you, and you should work with your Cohesity team to size any solution to fit your environment. But if you’re running Cohesity in your environment already, talk to your account team about how you can leverage the virtual edition. It really is pretty neat. I’ll be looking into the resiliency of the solution in the near future and will hopefully be able to post my findings in the next few weeks.

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